Electric valve excitation circuit



Dec. 26, 1950 A. SCHMIDT, JR 2,535,698

ELECTRIC VALVE EXCITATION CIRCUIT Filed Dec. 28, 1949 inventor": AugustSchmidt, Jr?

His At torn ey Patented Dec. 26. 1950 ELECTRIC VALVE EXCITAT ION CIRCUITAugust Schmidt, Jr., Schenectady, N. Y., assignor to General ElectricCompany, a corporation of New York Application December 28, 1949, SerialNo. 135,352

1 Claim.

This invention relates to electric valve excitation circuits and moreparticularly to an excitation circuit for continuously excitingelectronic devices utilizing an ionizable medium.

For certain purposes, it is desirable to excite continuously theionizable medium used in electronic devices such as ignitron tubes. Inorder to maintain the cathode spot, it has been necessary to supply arelatively large current to the holding anode element such as isutilized in devices of the mercury pool cathode type. Ordinarily thislarge current would be larger than would be necessary under normalconditions to maintain the cathode spot in order that the spot would bemaintained during abnormal conditions. Such large currents eitherrequire an excitation circuit made up of relatively large componentparts or are characterized by high energy losses in the circuit.

An object of this invention is to provide static means for controllingin a precise fashion the excitation of a continuously energizedelectronic device having an enclosing envelope containing an ionizablemedium.

Another object of the invention is to provide automatically operablemeans for limiting the energy required to maintain continuously thecathode spot in an electronic device of the type which utilizes anionizable medium such as mercury.

Still another object of the invention is the provision of an arrangementfor automatically reestablishing the excitation of an electronic deviceof the continuously excited ionizable medium type should the devicemomentarily become deenergized.

In accordance with my invention, the flow of current from the holdinganode of the cathode spot is utilized to control a variable impedanceconnected in series with the ignitor element and the components arearranged so that the impedance in series with the ignitor is promptly decreased by a substantial amount should current cease to flow from theholding anode to the cathode. In this way, the ignitor is promptlyreenergized and the cathode spot reestablished.

While I have shown my invention as applied to an electronic device ofthe well known ignitron type, it will be understood that it is notlimited thereto and that the invention can be used in conjunction withany electronic device having an enclosing envelope with an ionizablemedium and a holding anode disposed therein.

My invention will best be understood by reference to the accompanyingdrawing in which the numeral I represents the enclosing envelope of anelectron device of the ignitron type. A metallic closure 2 is joined tothe envelope I] through insulating ring 3. Closure 2 forms a part of thecathode. Also disposed within the envelope are a main anode 4, a controlgrid 5, a holding anode 6 and an ignitor 'I.

As is well known, flow of current through the ignitor circuit vaporizesthe mercury pool contained in metallic closure 2 and the spot soestablished on the mercury pool is maintained by the holding anode 5which is of such a potential with respect to the cathode that a flow ofelectrons is maintained from the cathode to the anode 8.

For energizing ignitor 'I, a transformer 8 energized from a source ofalternating current potential 9 is used. The secondary winding oftransformer 8 is arranged in series with the ignitor I, and aunidirectional conducting device ID prevents the flow of current fromignitor I to transformer 8 through device Ill. Also included in theexcitation circuit for ignitor I is a winding II forming a part of avariable reactor I2 having a magnetizing winding l3 and a controlwinding I4. Direct current potential for the holding anode 6 is suppliedby rectifier I5 and transformer I6 from the alternating current supply9. A suitable current limiting resistor I1 is connected in series withthe holding anode 6.

The magnetizing winding I3 and the holding winding I4 are oppositelywound and are constructed of a proper number of turns so that themagnetomotive force produced by winding I3 is partially or completelyofiset by the magnetomotive force of winding I4 if holding anole 6 andits associated circuit is conducting a current, i. e. when a cathodespot is being maintained on the surface of the mercury pool. Magnetizingwinding I3 is constructed so that the reactor I2 will become saturatedshould a current cease to flow in winding I4. In this way, the reactanceof winding II is substantially reduced upon failure of current to flowfrom holding anode 6 to the mercury pool. This substantial reduction inthe overall impedance of winding I I results in a relatively largecurrent through ignitor I and its associated circuit from the secondaryoi transformer 8. This large current is of sufficient magnitude toreestablish the cathode spot should the holding anode fail momentarilyto maintain this spot.

Since the arrangement shown in the drawing and described thus far iscapable of automatically reestablishing the cathode spot, it is notnecessary to supply a large current through the holding anode 6 and itsassociated circuit. Thus a minimum of current is required through thiscircuit and the component parts thereof can be of a relatively smallsize without incurring substantial energy losses in the holding anodecircuit.

While I have shown and described a particular embodiment of myinvention, it will be obvious to those skilled in the art that variouschanges and modifications may be made without departing from myinvention in its broader aspects, and I, therefore, intend in theappended claim to cover all such changes and modifications as fallwithin the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

In combination, an electric discharge device of the type employing anenclosing envelope and comprising therein an ionizable medium, acathode, an ignitor, and a holding anode, an energizing circuitconnected to said ignitor for causing the emission of electrons by saidcathode, saturable impedance means connected in said circuit, meansincluding a source of direct current for energizing said holding anode,a magnetizing Winding energized with direct current and effective tosaturate said impedance means, and a control winding the energization ofwhich is dependent upon the flow of current from said holding anode tosaid cathode for opposing the magnetizing efifect of said magnetizingWinding.

AUGUST SCHMIDT, J R.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 20 2,426,046 *Pakala Aug. 19,1947 2,441,987 Boyer et a1 May 25, 1948

